1. Field of the Invention
The present invention relates to integrated circuit products and, more particularly, to a method and apparatus for reducing the programming time for antifuse elements in such products.
2. Description of the Prior Art
Contemporary memory products require a high degree of redundancy in order to improve manufacturing yields. Present redundancy techniques in memories include providing extra columns and/or extra rows in the memory arrays. These extra columns and rows can be used to replace defective columns, rows, or single bit failures.
Antifuses have been used as nonvolatile programmable memory elements to store logic states used in memories for row and column redundancy implementation. An antifuse is a device that functions as an open circuit until programmed. By way of example, antifuses for redundancy implementation on a dynamic random access memory ("DRAM") are usually constructed in the same manner as the memory cell capacitors in the DRAM array. When programmed, an antifuse creates a short circuit or low resistance link, thereby enabling the particular redundant row, column, or memory location.
Antifuses have other uses in integrated circuit products besides redundancy implementation. Antifuses may, for example, be used in integrated circuits as a mechanism for changing an operating mode. Likewise, antifuses may be programmed to encode identification information about the integrated circuit, such as when the integrated circuit was fabricated.
A semiconductor die often contains a plurality of antifuse elements as shown, for example, in U.S. Pat. No. 5,301,143, which is assigned to the assignee of the present invention and which is incorporated herein by reference for all purposes. Additionally, the number of antifuses in a DRAM has increased as the density of DRAMs has increased. For example, a 4 M DRAM may have over 100 antifuses, while a 64 M DRAM may have over 1600 antifuses. For this reason, the time that is required to program the antifuses in a DRAM has increased. Accordingly, a method and apparatus for reducing antifuse programming time would be beneficial.
The present invention is directed to overcoming, or at least reducing the affects of, one or more of the problems set forth above.